http://www.youtube.com/watch?v=jzp39LizZVw
That scene at the very end had me nearly in tears, and anyone who played MGS3 the first time around and understood, I guarantee they'll have felt the same.
The way the music climaxes as he salutes just gives me chills every time I see it, and the way you see this hardened soldier, who struggles to show any emotion throughout the mission, just cry like that got me the first time I saw it, and still does.
MGS, in my opinion, is the best game series out there today, purely for the story. The gameplay is unrivalled anyway, but a film series like this would have been majorly successful anyway.
The writing, the acting, the direction, the pace, it's all brilliant.